Heat-developable two-component diazotype reproduction material



Oct. 25, 1966 ENDERMANN ET AL 3,281,244

HEAT-DEVELOPABLE TWO-COMPONENT DIAZOTYPE REPRODUCTION MATERIAL Filed Jan. 24, 1963 LIGHT SENSITIVE LAYER II INVENTORS FRITZ ENDERMANN JOHANNES MUNDER HELLMUT ZIEGLER ATTORNEY United States Patent M 3,281,244 HEAT-DEVELOPABLE TWO-COMPONENT DIAZO- TYPE REPRODUCTION MATERIAL Fritz Endermann, Wiesbaden, Johannes Munder, Wiesbaden-Biebrich, and Hellmnt Ziegler, Wiesbaden- Schierstein, Germany, assignor, by mesne assignments,

to Keulfel & Esser Company, Hoboken, NJ.

Filed Jan. 24, 1963, Ser. No. 253,646 Claims priority, application Germany, Jan. 27, 1962, K 45,776 7 Claims. (Cl. 96-91) The present invention relates to diazotype reproduction materials and refers more particularly to heat-developable two-component diazotype reproduction material and to processes for preparing said materials.

For the preparation of prints by the diazotype process, two methods are in practice used, the so-called dry process and the so-called semi-wet process. In the dry process the reproduction material contains both a diazo compound and a coupler in the light-sensitive coating, and the development of the exposed reproduction material is effected in ammonia vapour. In the semi-wet process the reproduction material contains a diazo compound in the light-sensitive coating and during development in acid or alkaline solution a coupler is brought in contact with the exposed material so that in the parts of the coating unaffected by the light an azo dyestuff is formed as a result of coupling between the diazo compound and the coupler.

The development step in both processes has disadvantages such as the troublesome odors arising from the gaseous ammonia used in the dry process and the need for a coupler bath in the semi-wet process. These disadvantages apply to apparatus requirements also. Therefore attempts have been made to obtain a more simple development process by the action of steam or heat.

The coupling process of a diazo compound with a coupling component containing hydroxy groups takes place readily only in an alkaline to neutral pH region. Most experiments undertaken hitherto in the field of heat development have been directed towards the displacement of the pH value in the light-sensitive coating from the acid into the neutral or alkaline region by temperature increase, possibly with the help of certain additives. This can be done by the removal of a volatile acid or the development of substances with alkaline action from non-alkaline substances which are added to the light sensitive coating. Copies obtained in this way are, however, with respect to contrast and keeping qualities, inferior to the ammonia prints.

It has further been suggested that the coupling component and the diazo compound should be used in two layers separated from each other by a fusible third layer which would prevent premature coupling. The production of such a diazotype material is however very costly from the technical point of view because at least three layers have to be applied one after the other to the sup porting material and the middle one must moreover be absolutely impermeable and free of pores and therefore needs particularly careful attention.

Therefore one object of the present invention is to provide a diazotype reproduction material which does not have the disadvantages of prior art.

Another object is to provide a two-component diazotype reproduction material which is developable without the use of gaseous ammonia or a developer bath.

Another object is to provide a diazotype reproduction material which is developable by heat.

Another object is to provide a process of making a heatdevel-opable two-component diazotype reproduction material.

Another object is to provide a heat-developable two- 3,281,244 Patented Oct. 25, 1966 component diazotype reproduction material which has very good contrast, which has good keeping qualities, and which is easy to produce.

Another object is to provide a diazotype reproduction material which, in addition to being heat-developable, is applicable in thermographic processes and, after generation of an image by imagewise heating, can be fixed by exposure to light.

Other objects will become apparent from the specifications and claims.

The drawing shows a cross-sectional view of a base and a light-sensitive layer on said base.

The present invention relates to a heat-developable diazotype reproduction material containing a conp-ler in the light-sensitive coating in addition to a diazo compound, which material has advantages over the known reproduction materials of this type. It is characterized by the fact that the coupling component is a substance which has acid action resulting from a phenolic or enolic hydroxy group and which forms an intimate mixture with an equivalent quantity of alkali hydroxide and/or alkaline earth hydroxide, the mixture being in the form of tiny particles which are enveloped in a water-insoluble organic substance that melts at between 50 and 200 C.

For the preparation of the diazotype reproduction material provided by the invention, the finely pulverized mixture of the coupling component with an equivalent quantity of alkali hydroxide or alkaline earth hydroxide may, for example, be introduced into the melt of a suitable Wax or resin and the melt allowed to solidify with the particles of mixed coupler and alkali or alkaline earth hydroxide suspended therein. The solidified substance is then finely pulverized and the powder washed with a solvent, preferably water, to remove any outwardly adhering coupler and alkali or alkaline earth hydroxide not enveloped. The washed powder may then be applied from an aqueous suspension together with one or more suitable water-s-olu-ble diazo compounds and the additives commonly used in diazotype processes to a suitable base, support, or supporting material, such as paper, viscose foil, cellulose, acetate foil, etc., in a single process to produce a coated material as in the figure which material comprises a base 10 and a layer 11 on said base.

Another process for the preparation of a heat-developed diazotype reproduction material provided by the invention comprises a finely pulverized intimately mingled mixture of a substance with acid action resulting from a phenolic or enolic hydroxy group with an equivalent quantity of alkali metal hydroxide and/or alkaline earth metal hydroxide being dispersed in a solution of a waterinsoluble organic substance that melts at between 50 and 200 C., the dispersion being atomized and dried, the resultant fine powder being washed with a solvent, preferably water, and suspended in an aqueous solution of the diazo compound and the suspension being coated upon the supporting material.

The atomizing and drying of the dispersion may, for example, be carried out in a wide vertical shaft into which the dispersion i introduced from above via a jet while a current of hot air or other hot gas is introduced from below to meet the falling atomized droplets. The hot current of gas rapidly evaporates the solvent from the droplets so that the dispersed material falls to the bottom in solid particles in the form of a fine dust. By another spray-drying process the dispersion is made to drip in a closed container upon an atomizing plate which is rotating very rapidly, e.g., 5000 to 20,000 revolutions per minute, which causes the liquid to become atomized. The atomized particles are dried by a current of hot gas that is passed through the container and the material is then obtained in the form of a fine powder. The said processes can be modified in a multitude of ways. For

example, the spray-drying may be carried out in a medium of very high air or gas pressure. The hot gas is, for example, often passed to the drying dispersion not in a counter-current, but in a current travelling in the same direction.

In the diazotype reproduction material provided by the invention, the coupling component in the form of tiny particles enveloped in the coating of wax or resin or similar material is preferably used in a maximum grain size of 30 microns. If coarser powder is used it becomes difficult to obtain evenly coated diazotype reproduction material accordant with the invention. Separation of the fraction with the desired particle size is carried out in known manner, e.g. by screening or air-sifting.

In the diazotype reproduction material provided by the invention the coupling reaction between the coupling component and the diazo compound does not take place until the water-insoluble skin which envelops each particle of the mixture of coupler and alkali hydroxide or alkaline earth hydroxide is melted by the action of heat.

For the skin which envelops the coupler component, water-insoluble organic substance are suitable, provided they have melting range within the region of 50 to 200 C., are colorless or only weakly colored, are fluid in their molten states, and are sufficiently hard and brittle at room temperature to enable them to be finely pulverized and do not react with the diazo compounds used. For example, wax or resin-type substances fulfilling these condiitons may be used. This includes natural resin such as colophony, root resins, and shellac, conversion products of natural resins, such as hydrogenated resins, calcium and zinc resinates, resin esters and ynthetic resins moditied with natural resins, maleic resins, oil-free alkydresins, light-colored phenol resins of the novolak type, alkyl phenol resins and terpenephenol resins, coumarone resins, vinyl polymers such as polyvinyl acetals, polyvinyl acetates, polyvinyl chloride, polyvinylidene chloride, polyvinyl ether, polyacrylic acid ester, polystyrene and interpolymers of the vinyl compounds with one another and with other polymerizable compounds, polymers of aliphatic unsaturated hydrocarbons, ketone resins, chlorodiphenyl resins, epoxy resins and silicone resins. Among substances having melting ranges in the lower portion of the temperature range given above, those with a narrow melting range, e.g. of not more than 10 C., are preferred.

As the coupling component in the reproduction material provided by the invention, practically any organic compound with phenolic or enolic hydroxyl groups can be used which in the presence of the alkali hydroxide or alkaline earth hydroxide provided in accordance with the invention is able to couple, at least when heated, with the diazo compound to form a dyestuif. The following example are given:

2,3-dihydroxynaphthalene,

acetoacetic anilide, 2,3-dihydroxynaphthalene-6-sulphonic acid, 2-naphthol-3-carboxylic acid, Z-naphthol-S-carboxylic acid methyl ester, 2,4-dihydroxy benzamide, 1-methy13-hydroxy-benzene-4-glutaric acid, phenol-3-urea, 2,4,2,4-tetra-hydroxydiphenyl, l-phenyl-3-methyl-pyrazolone- 5 and resorcinol.

As the diazo compound, all diazo compounds used elsewhere in diazotype processes are suitable provided they are sufliciently stable in the temperature region of the heat development and in the presence of the quantity of alkali hydroxide or alkaline earth hydroxide to be used as provided by the invention and couple at least in the heat to form a dyestulf with a coupler of the type to be used as provided by the invention. Examples of such diazo compounds are: I

2,5-diethoxy-4-benzoylaminobenzene diazonium chloride;

4-phenyl-arninobenzene diazonium hydrogen sulphate; 4-diazo-2,5-dimethoxy-4'-methyldiphenyl-sulphide (HCl-salt); 4-morpholinobenzene diazonium fluoborate; 4-morpholino-2,S-diethoxybenzene diazonium-chloride; 4-morpho1ino-2,5-dimethoxybenzene diazonium chloride; 4-dimethylaminobenzene diazonium chloride; 4-(4'-ethoxyphenyl) -2,5-diethoxybenzene diazonium chloride; 4-ethylb'enzylaminobenzene diazonium chloride; 2-ethoxy-4-diethylaminobenzene diazonium chloride; and 4-benzylarnino-2,5-diethoxybenzene-diazonium chloride.

In addition to the diazo compound and the coupler, the additives usually included in diazotype materials such as tartaric acid or citric acid, zinc chloride and thiourea may also be present. Also, it is advantageous in the preparation of the reproduction material for a wetting agent such as saponine to be added so that the particles of coupler enveloped in the water-insoluble skin may be better suspended in an aqueous solution of the diazo compound. It is also advantageous for a binder such as carboxyl methyl cellulose, soluble starch, casein, gelatine or synthetic resin dispersions to be used to ensure that the particles adhere firmly to the supporting material. Base papers such as are commonly used in diazo printing may be used as supports, but also transparent foils made of various materials, e.g., processed cellulose products such as cellulose hydrate or cellulose esters or of synthetics such as polyamides, polyesters, polycarbonates and polyvinyl compounds are suitable. The preference is, however, for paper and similar cellulose products.

For the preparation of copies, the reproduction material provided by the inventi-on is exposed under a master in known manner and then brought into contact with a hot body, e.g., a hot roller or plate. A heat image can also be produced by the contact process with the reproduction material provided by the invention if a master with an image on one side only is placed between an infrared source and the reproduction material provided by the invention in such a way that the image-side of the master and the non-sensitized side of the light-sensitive reproduction material are in contact. Under the influence of the infra-red rays the image parts of the master generate more heat than the image-free parts. With a suitable dosage of radiation this heat will be sufiicient to melt the water-insoluble skin enveloping the particles of mixed coupler and alkali hydroxide or alkaline earth hydroxide in the reproduction material in the parts adjacent to the image parts, so that a coupling image is produced in the reproduction material. The images are fixed by exposure to light, the unused diazo compound left in the image-free parts being thereby decomposed.

A third method whereby copies can be produced is the reflex process. The reproduction material accordant with the invention is placed between the infra-red source and the master in such a Way that the image side of the master and the non-sensitized side of the light-sensitive material are in contact. The master may in this case have images on both sides. The infra-red rays are then reflected in the image parts and cause heating and consequent formation of a heat-coupling image. In this case too the unused diazo compound in the image-free parts of the reproduction coating is decomposed by subsequent exposure to light.

Reproduction coatings accordant with the invention have the advantage that they are simple to produce. They can be developed by a mere heating process, i.e., without any adjuvant such as alkali or steam, give prints with very good contrast and have good keeping qualities.

Example 14.8 parts by weight of resorcinol and 15.6 parts by weight of potassium hydroxide were Well dried and then finely ground. They were then suspended, with stirring, in 50 parts by weight of melted carnauba wax (melting temperature: 83 to 91 C.) at 140 to 150 C. After complete homogenization the material was cooled rapidly to avoid disintegration and the solidified melt was broken up and ground in a ball mill. Any coupling substance not enveloped which may be adhering to the particles was removed by repeated washing with water. The fraction with the most favourable particle size of not more than 30 microns was separated by drying and subsequent screening or air-sifting.

The following aqueous suspension was then applied to a supporting material of, e.g., paper:

parts by weight of wax-enveloped coupling powder 2 parts by weight of 4-benzylamino-2,5-diethoxybenzene diazonium-chloride 8 parts by weightof thiourea 2 parts by weight of citric acid 0.02 part by weight of saponine 3.5 parts by weight of casein 70 parts by Weight of water The supporting material coated with the suspension was dried at 30 to 40 C. in a current of air. A coupling image was then produced in a heat-copying apparatus as follows. A master with text on one side only was placed between the infra-red source and the reproduction material in such a way that the text of the master and the nonsensitized side of the reproduction material were in contact. The unused diazo compound was then decomposed by exposure to light. In this way a red copy correspond ing to the master was obtained.

It is apparent that the described example is capable of many variations and modifications within the scope of the present invention. All such variations and modifications are to be included within the scope of the present invention.

What is claimed is:

1. A heat-developable two-component diazotype repro duction material, which comprises a support and a lightsensitive diazo layer coated on said support, said layer comprising a light-sensitive diazonium compound, an enolic coupling component, an hydroxide selected from the group consisting of alkali hydroxides and alkaline earth hydroxides, and an envelope substance, said coupling component and said hydroxide being enveloped together in the unreacted state in about equivalent amounts without any liquid in said substance and intimately, uniformly dispersed with said diazonium compound throughout said layer in the form of particles having a maximum size of thirty microns, said substance melting between 50 C.

and 200 C., being fluid in its molten state and pulverizable at room temperatures, and unreactive with said diazonium compound.

2. A material in accordance with claim 1 in which said coupling component is selected from the group consisting of: 2,3-dihydroxy-naphthalene; acetoacetic anilide; 2,3- dihydroxy-naphthalene-6-sulfonic acid; 2-naphthol-3-carboxylic acid; 2-naphthol-3-carboxylic acid methyl ester; 2,4-dihydroxy-benzamide; 1-methyl-3-hydroxy-benzene-4- glutaric acid; phenol-3-urea; 2,4,2,4-tetra-hyd.roxy-diphenyl', 1-phenyl-3-methyl-pyrazolone-(5); and resorcinol.

3. A material in accordance with claim 1 in which said coupling component is resorcinol, said hydroxide is potassium hydroxide and said substance is carnauba wax.

4. A material in accordance with claim 1 in which said coupling component is 2,3-dihydroxy-napthalene, said hydroxide is potassium hydroxide, and said substance is carnauba wax.

5. A material in accordance with claim 1 in which said coupling component is 2,4-dihydroxy-benzamide, said hydroxide is potassium hydroxide, and said substance is carnauba wax.

6. A material in accordance with claim 1 in which said coupling component is 2,4,2,4'-tetrahydroxy-diphenyl, said hydroxide is potassium hydroxide, and said substance is carnauba wax.

7. A material in accordance with claim 1 in which said coupling component is 1-phenyl-3-methyl-pyrazolone-(5), said hydroxide is potassium hydroxide, and said substance is carnauba wax.

References Cited by the Examiner UNITED STATES PATENTS 2,846,309 8/ 1958 Land.

2,939,009 5/ 1960 Tien.

3,016,308 1/ 1962 Macaulay.

3,111,407 11/ 1963 Lindquist et a1 9675 X 3,113,865 12/1963 Sagura et al. 96-49 3,202,510 8/1965 Hollmann 9649 X FOREIGN PATENTS 1,041,980 10/ 1958 Germany.

815,005 6/1959 Great Britain.

NORMAN G. TORCHIN, Primary Examiner.

I TRAVIS BROWN, Examiner.

R. L. STONE, A. D. RICCI, Assistant Examiners. 

1. A HEAT-DEVELOPABLE TWO-COMPONENT DIAZOTYPE REPRODUCTION MATERIAL, WHICH COMPRISES A SUPPORT AND A LIGHTSENSITIVE DIAZO LAYER COATED ON SAID SUPPORT, SAID LAYER COMPRISING A LIGHT-SENSITIVE DIIAZONIUM COMPOUND, AN ENOLIC COUPLING COMPONENT, AN HYDROXIDE SELECTED FROM THE GROUP CONSISTING OF ALKALI HYDROXIDES AND ALKALINE EARTH HYDROXIDES, AND AN ENVELOPE SUBSTSANCE, SAID COUPLING COMPONENT AND SAID HYDROXIDE BEING ENVELOPED TOGETHER IN THE UNREACTED STATE IN ABOUT EQUIVALENT AMOUNTS WITHOUT ANY LIQUID IN SAID SUBSTANCE AND INTIMATELY, UNIFORMLY DISPERSED WITH SIAD DIAZONIUM COMPOUND THROUGHOUT SAID LAYER IN THE FORM OF PARTICLES HAVING A MAXIMUM SIZE OF THIRTY MICRONS, SAID SUBSTANCE MELTING BETWEEN 50*C. AND 200*C., BEING FLUID IN ITS MOLTEN STATE AND PULVERIZABLE AT ROOM TEMPERATURES, AND UNREACTIVE WITH SAID DIAZONIUM COMPOUND. 